It is known to use adhesives to provide a bond between shingles on a roof. Some shingle adhesives are made with blends of asphalt and polymer. During a typical shingle manufacturing process, a pattern of adhesive is applied to the headlap portion of the shingles, so that the tab portion of the subsequently laid course of shingles on the roof will adhere to the headlap portion of the lower course. The adhesive bond helps to prevent wind uplift of the shingles on the roof. It is also known to use adhesives to provide a bond between overlay and underlay portions of a laminated shingle.
U.S. Pat. No. 5,278,207 to Kluttz discloses a composition which may be used as an adhesive on a roofing material. The composition includes asphalt, a polyfunctional amine having at least two amino groups, a polymer such as SBS elastomer, and a crosslinker such as sulfur. The polyfunctional amine is said to be critical to prevent separation of the polymer from the asphalt. There is no suggestion to use a phenolic resin or a phenol-aldehyde resin as a crosslinker in a shingle adhesive.
U.S. Pat. No. 5,256,710 to Krivohlavek discloses a composition including an asphalt, a polymer, and a crosslinker which is either a phenolic resin or a phenol-aldehyde resin. There is no suggestion to use the composition as a shingle adhesive or other type of adhesive.
U.S. Pat. No. 5,270,361 to Duong et al. discloses a composition made from asphalt, natural or synthetic rubber, and selenium as a crosslinker. The patent states that the composition can be used for paving or shingles, but there is no suggestion to use the composition as a shingle adhesive or other type of adhesive.
It would be desirable to provide an improved shingle adhesive having consistency of performance, heat stability, ability to be handled in bulk, flexibility in the choice of asphalt used, and resistance to flattening under the pressure exerted by stacked shingles.
The above objects as well as others not specifically enumerated are achieved by an improved adhesive for a roof covering in accordance with the present invention. The adhesive comprises asphalt, polymer and crosslinker. In a first embodiment of the invention, the crosslinker is a phenolic resin or a phenol-aldehyde resin.
In a second embodiment, the adhesive comprises asphalt, polymer and crosslinker, and it excludes polyfunctional amine having at least two amino groups.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings.
The present invention uses crosslinking technology to create a modified asphalt adhesive having desirable properties for use on roof coverings such as shingles. In particular, the adhesive has excellent compatibility between the asphalt and the polymer, and excellent thermal stability at elevated temperatures. These attributes improve the consistency of performance of the adhesive, allow for bulk transport of the adhesive, and increase the number of asphalts that are usable in the adhesive. The adhesive also has the ability to maintain its shape under the high pressure exerted by stacked shingles. The adhesive retains good bond strength at low temperatures, so that it meets the needs of shingles in cold climates.
The adhesive includes an asphalt, a polymer and a crosslinker. It has been found that an adhesive having the desired properties can be achieved by the choice of a suitable crosslinker and polymer. This contrasts with the above-mentioned Kluttz patent, which states that a particular polyfunctional amine is critical to prevent separation of the polymer from the asphalt. The adhesive of the present invention has excellent compatibility so that it is highly resistant to separation even without the addition of a polyfunctional amine.
The asphalt for use in the adhesive can be either a naturally occurring asphalt or a manufactured asphalt, such as an asphalt produced by refining petroleum or by other known means. Mixtures of different asphalts can also be used. Advantageously, the improved compatibility between the asphalt and the polymer allows increased flexibility in the type of asphalt used in the adhesive. Preferably, the asphalt is a paving grade asphalt or a roofing flux, or a blend of one of these with a solvent extracted asphalt such as a propane deasphalted asphalt (xe2x80x9cPDAxe2x80x9d). In a particular embodiment, the asphalt is a blend of paving grade asphalt and PDA.
The polymer for use in the adhesive can be any polymer suitable for combining with the asphalt and crosslinker to provide an adhesive having the desired properties. Mixtures of different polymers can also be used. Preferably, the polymer has double bonds which provide bonding sites for the crosslinker. Also preferably, the polymer is a thermoplastic elastomer such as a block copolymer, usually triblock (Axe2x80x94Bxe2x80x94A), and either linear or radial in structure. Either block, A or B, may comprise more than one monomer. Preferred are those triblock copolymers having styrene or polystyrene as the xe2x80x9cAxe2x80x9d block or end block units. Suitable elastomers include thermoplastic rubbers of styrene-butadiene-styrene (Sxe2x80x94Bxe2x80x94S) and styrene-isoprene-styrene (Sxe2x80x94Ixe2x80x94S) block copolymers. Suitable elastomers are commercially available from Kraton Polymers (Houston, Tex.) as KRATON(trademark) thermoplastic rubbers, KRATON D grade. Most preferred is KRATON D-4158 (Sxe2x80x94Bxe2x80x94S) thermoplastic rubber, a radial block copolymer which contains paraffinic oil as an extender.
The crosslinker for use in the adhesive can be any crosslinker suitable for combining with the asphalt and polymer to provide an adhesive having the desired properties. Mixtures of different crosslinkers can also be used. Some examples of suitable crosslinkers include sulfur crosslinkers and silane coupling agents such as those available from Harwick Chemical Corp., Akron, Ohio under the trade names Harwick DSC-45 (tetrasulfide organo-functional group), DSC-25 (mercapto) and DSC-30 (polysulfide). A highly preferred crosslinker for use in the adhesive is a phenolic resin or a phenol-aldehyde resin, such as disclosed in U.S. Pat. No. 5,256,710 to Krivohlavek, issued Oct. 26, 1993 (incorporated by reference herein). A crosslinker as described in the Krivohlavek patent is commercially available as BUTAPHALT(trademark) from TexPar Energy, Sandy, Utah. BUTAPHALT was registered in 1997 to Asphalt Technology and Consulting, Inc., Oklahoma (Registration No. 2040669).
The adhesive can optionally include other ingredients commonly used in shingle adhesives, in concentrations taught in the art, such as fillers, stabilizers, antioxidants, pigments, and solvents.
The composition of the adhesive will often vary depending on the use of the adhesive. When the adhesive is used as a sealant for three-tab shingles, preferably the adhesive comprises, by weight, about 85% to about 95% asphalt, about 5% to about 15% polymer and about 0.05% to about 2% crosslinker. Typically, the adhesive comprises about 88% to about 94% asphalt, about 6% to about 12% polymer and about 0.05% to about 1% crosslinker. In a particular embodiment, the adhesive comprises less than 9% polymer and greater than 0.1% crosslinker. When the adhesive is used as a laminating adhesive to make laminated shingles, preferably the adhesive comprises, by weight, about 90% to about 97% asphalt, about 3% to about 10% polymer and about 0.05% to about 1% crosslinker.
An example of a preferred adhesive for use as a sealant for three-tab shingles has the following composition:92% Asphalt (blend of paving asphalt and PDA) 8% KRATON, 41580.2% BUTAPHALT. Conventional mixing or blending techniques can be used to make the adhesive. Typically, the ingredients are mixed for at least about four hours. Generally, throughout the mixing, the temperature is desirably maintained from about 260xc2x0 F. to about 360xc2x0 F. The adhesive is either shipped and used in bulk without cooling, or cooled in packages and then melted for application to shingles or other roof covering.
The adhesive can be applied to any type of roof covering, such as three-tab shingles, laminated shingles, roll roofing, built-up roofing, or non-asphalt based roof coverings such as wooden or slate shingles. The adhesive can be applied by conventional application techniques. Different roof coverings and application techniques are well known in the art. For example, U.S. Pat. No. 4,738,884 to Algrim et al., issued Apr. 19, 1988 (incorporated by reference herein) discloses an adhesive applied to three-tab shingles. U.S. Pat. No. 6,014,847 to Phillips, issued Jan. 18, 2000 (incorporated by reference herein) discloses using a laminating adhesive to attach the underlay to the overlay of a laminated shingle.
In a typical application, the adhesive is applied in a pattern on the headlap portion of a three-tab shingle for use as a sealant. The adhesive is usually applied as a bead which protrudes a short distance from the surface of the shingle. When the shingle is installed on a roof, the tab portion of the upwardly adjacent shingle is pressed against the adhesive bead to bond the tab portion, thereby helping to prevent wind uplift of the tab portion.
In another application, the adhesive is used for laminating shingle parts together to make a three dimensional looking shingle. The compatibility, stability and strength properties of the adhesive, as discussed herein, are also of value in this application.
The adhesive has excellent compatibility between the polymer and the asphalt, so that it is highly resistant to separation of the polymer from the asphalt even after storage at elevated temperature. The resistance to separation can be tested by placing a sample of the adhesive in a cigar-shaped tube and storing the tube vertically at 350xc2x0 F. for 24 hours. The tube is then cooled to room temperature, and the sample is removed from the tube. The top third of the sample and the bottom third of the sample are each tested for softening point by the conventional ring and ball method. If the softening point of the top of the sample is substantially greater than the softening point of the bottom of the sample, this indicates that a significant proportion of the polymer has separated from the asphalt and risen to the top of the tube (because the polymer is lighter than the asphalt). On the other hand, if the top and bottom softening points are not substantially different, this indicates that little separation of the polymer from the asphalt has occurred. Preferably, the adhesive has a difference in softening point of less than about 35xc2x0 F. between the top and the bottom of the adhesive, and more preferably less than about 30xc2x0 F. Of course the resistance to separation, like any other parameter mentioned in this application, can be measured by any other suitable test.
As discussed above, when used as a sealant, the adhesive is often applied to shingles in the shape of a bead which protrudes a short distance from the surface of the shingle. A problem that can occur during storage of shingles is that the adhesive bead becomes flattened under the high pressure exerted by the stacked shingles, reducing the ability of the bead to bond the shingles together on the roof. Advantageously, the adhesive of the invention is sufficiently firm so that it maintains its shape under the high pressure exerted by stacked shingles. Preferably, the adhesive has a Brookfield viscosity at 350xc2x0 F. between about 300 centipoise and about 1000 centipoise. The viscosity needs to be low enough to allow pumping and application but high enough to maintain bead height while cooling on the sheet. Preferably, the adhesive has a penetration at 77xc2x0 F. between about 25 dmm and about 40 dmm. Too soft an adhesive may be too tacky and lack resistance to flow while too hard a bead may not have the proper activation temperature. The penetration is measured by ASTM D5. Preferably, the adhesive has a softening point between about 180xc2x0 F. and about 220xc2x0 F. to allow proper bead height and also good activation temperature.
The bond strength of the adhesive is evaluated using ASTM D 6381 by sealing at a variety of temperatures and testing at a variety of temperatures. It is desired to have good bond strengths over a range of both sealing temperature and testing temperature. Preferably, the adhesive has a bond strength after sealing at 140xc2x0 F. that is greater than 3 lbs. at 0xc2x0 F. and greater than 10 lbs. at 77xc2x0 F. Preferably, the adhesive even seals at 100xc2x0 F., and has a bond strength after sealing at 100xc2x0 F. of at least 3 lbs. at 77xc2x0 F.